docs: def set_config(self, key, option, value):
          """Set a configuration option for a key"""
          if '_config' not in self.proxy:
              newopt = dict(default_cfg)
              newopt[option] = value
              self.proxy['_config'] = {key: newopt}
          else:
              if key in self.proxy['_config']:
                  self.proxy['_config'][key][option] = value
              else:
                  newopt = dict(default_cfg)
                  newopt[option] = value
                  self.proxy['_config'][key] = newopt